TheAMCForum.com Homepage
Forum Home Forum Home > The Garage > AMC V8 Engine Repair and Modifications
  New Posts New Posts RSS Feed - 390 engine
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Click for TheAMCForum Rules / Click for PDF version of Forum Rules
Your donations help keep this valuable resource free and growing. Thank you.

390 engine

 Post Reply Post Reply Page  <12
Author
Message
rodhhrod View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/11/2010
Location: Oregon
Status: Offline
Points: 1040
Post Options Post Options   Thanks (0) Thanks(0)   Quote rodhhrod Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 11:09am
All numbers check good and it does say 390 on it. Too bad, pulled a head off yesterday and has 60 over pistons in it. So much for original, damn, not sure what I am going to do now.
Back to Top
jpnjim View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Nov/25/2007
Location: New England
Status: Offline
Points: 2752
Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 12:44pm
+.060" is a lot for a 390/401,
but have the walls sonic tested before freaking out.

Factory spec says +.023 max,
rule of thumb says +.030" max,
but others have gotten away with more

+.060 = 4.225, but you don't know how thin the walls are until they're checked.

You could always list it for what you have in it,
hopefully the crank isn't +.030 already too 
^though even then the crabk can go .050+ on the mains, and the rods can go even more depending on what you're building.
71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
Back to Top
70amxvegas View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Apr/26/2009
Location: Lost Wages
Status: Offline
Points: 1791
Post Options Post Options   Thanks (0) Thanks(0)   Quote 70amxvegas Quote  Post ReplyReply Direct Link To This Post Posted: Oct/18/2017 at 2:26pm
60 over is ok .I bet there are a lot of them out there 60 over
Back to Top
farna View Drop Down
Supporter of TheAMCForum
Supporter of TheAMCForum
Avatar
Moderator Lost Dealership Project

Joined: Jul/08/2007
Location: South Carolina
Status: Offline
Points: 19610
Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2017 at 6:01am
For a race engine 0.060" over might be okay, but thin cylinder walls mean higher temps, and a street 390/401 bored that much will likely have heating/cooling issues if driven any length of time. Not so important for drag cars -- can take time to cool between runs, and runs only last a few seconds.

jpnjim -- My best guess is the 401 as created because of competition more than anything else. Abernethey had set AMC up to compete head to head with the big three, and wanted to push AMC up into the mid priced segment (Buick/Olds/Pontiac/Mercury territory), and the competition all had 400 cubic inch engines. The upcoming changes in emissions/lower compression may have had something to do with it though, as cubic inches can make up for lower compression.
Frank Swygert
Back to Top
rodhhrod View Drop Down
AMC Addicted
AMC Addicted
Avatar

Joined: Jul/11/2010
Location: Oregon
Status: Offline
Points: 1040
Post Options Post Options   Thanks (0) Thanks(0)   Quote rodhhrod Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2017 at 4:55pm
The saga continues on the 390, Question- on the drivers side the piston notches are all facing forward on the upper left about 10 oclock. The passenger side the notch  are facing forward but on the lower right section about 5 o'clock. is this common or is there a screw up here. According to the TSM the notch should be upper forward. Sure could use some help here.
Rod
Back to Top
 Post Reply Post Reply Page  <12
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.113 seconds.
All content of this site Copyright © 2018 TheAMCForum unless otherwise noted, all rights reserved.
PROBLEMS LOGGING IN or REGISTERING:
If you have problems logging in or registering, then please contact a Moderator or